The present invention is generally directed to a method of filling and sealing undesired underground openings with use of a grouting material. While the invention is applicable to a number of such underground filling and sealing applications, the filling and sealing of openings in karstic terrain and in mines is of particular interest.
For many years, attempts have been made to close off karstic terrain to prevent undesirable water flow through the terrain. Such water flow causes flooding and/or surface collapse. Karstic terrain is most commonly observed in areas in which predominantly limestone geology has functioned to create underground voids and sink holes at the surface of the ground. Karstic terrain typically contains caves and caverns.
Karst or karstic zones are formed over millions of years when rainfall, which is commonly acidic, flows into cracks and fissures in the ground and contacts limestone bedrock located below the surface of the ground. The contact of acidic rain with the alkaline limestone rock causes two primary actions; namely, (1) corrosion of the rock due to an acid/alkaline reaction; and (2) erosion caused by the abrasive action of water wearing through the rock. The effect of these two actions, over time, creates pathways through the rock thereby forming caves and caverns in a random fashion along with underground water streams. Such created voids and pathways can vary from small cracks to voids of enormous volume. Some of the voids and pathways are located many hundreds of feet below ground but are always connected to the surface due to the method of creation.
Some portions of a given karstic terrain may become filled with clays or fines created by the washout, and thus appear to be normal ground. As time, weather, hydrology, and ground movement occur, the nature of these filled areas often changes abruptly and surface anomalies, such as sink holes, are formed. Often these surface anomalies create problems above ground involving building subsidence and foundation compromise. Underground operations, such as mining, may be impaired or rendered inoperable because of water inundation or the collapse of supporting structures.
The above-mentioned problem exists on a worldwide basis with regions located in many areas including Slovenia, Italy, Ireland, Germany, Israel, Madagascar, China, Japan, Australia, New Zealand, the Caribbean, Canada, and the United States. Many states of the United States, including Florida, New Mexico, Kentucky, Missouri, and Arkansas have karst regions. It has been estimated that about 25% of the United States has karst regions. In recent years, karst formation is believed to have accelerated due, in part, to industrialization and airborne pollutants causing more acutely acidic rain.
Another application for practice of the method of the present invention is that of filling and sealing water-filled portions of underground mines such as coal mines, ore mines, salt mines, etc. Sealing of such portions permits water to be pumped out of such portions, the portions to be repaired, and the subsequent reuse of such portions.
Many attempts have been made to solve the above-mentioned problems with use of traditional grouting methods such as cement grouting, bentonite grouting, bitumen grouting, and various types of chemical grouting. Inevitably, such attempts become abandoned because of the expense of these methods and the unknown extent of the karst region. Although temporary fixes are common, subsequent failure almost invariably occurs. Further attempts to fix the problem are usually not made because of the uncontrollable effectiveness of most of these methods and the associated high costs.
As demonstrated from the above discussion, there is a long standing problem in the art which has not been satisfactorily addressed to date. The present invention is believed to address and solve such long standing problem in the art by providing a novel method of grouting that is both effective in terms of speed of deployment and use of materials and results in the effective filling and sealing of huge volumes of underground voids or openings. As will become apparent from the following description, the method of the invention is believed to provide a quickly deployed, cost effective solution to a substantial problem by creating an underground opening filled and sealed with a grout comprising aggregate coated with an expanded hydrophobic polymeric resin.